Metal-boring tool



(NoModeL) G. W. TOWER; METAL BORING TOOL.

No. 359,296. Patentd Mar. 15, 1887;

F751. WITNESSES.

n, vtrzns mmummw. Wnhlngton. n. c

UNITED STATES PATENT @FFICE.

GEORGE V. TOWER, OF BOSTON, MASSACHUSETTS. I

. METAL-BORING TOOL.

SPECIFICATION forming part of Letters Patent No, 359,296, dated March15, 1887.

Application filed Drcemher H3, 1886. Serial No. 22l,810..

To aZZ whom it may concern.-

Be it known that I, GEORGE W. TOWER, a citizen of the United States,residing at Boston, in the county of Suffolk and State of Massachusetts,have invented certain Improvements in Metal-Boring Tools, of which thefollowing is a full, clear, and exact description, reference being hadto the accompanying drawings, making part of this specification, inwhich- Figure 1 is a perspective view of my improved metal-boring tool.Fig. 2 is a longitudinal section of the same. Fig. 3 isa transversesection of the same. Fig. 4 is an elevation of the front end of thesame.

My invention relates to certain improve ments in that class ofboring-tools which are used principally for boring large holes in metalplates, or where a smaller hole has been previouslymade boring a largerone from the same center to take its place; and my invention consists incertain novel combinations of parts and details of construction, ashereinafter set forth and specifically claimed, whereby a more effectiveand desirable tool of this character is produced than is now in commonuse.

In the said drawings, A represents the stock or main portion of theboring-tool, which is of cylindrical form, but may be of other shape, ifpreferred. This stock is provided at its rear end with a shank, b, whichis adapted to fit a corresponding socket in the machine employed forrotating the said tool, which can be used either with a hand or powermachine, ac-

cording to the nature of the work to be per- 4 5 f, within two oppositeones of which are placed the front end of the stock A in accordance (Nomodel.)

The bottoms of the pairs of grooves e and f 5:,

are at different distances from the center, and the grooves f areprovided with shoulders 71, whereby each of these latter grooves isadapted to hold a cutter at two different distances from the center, andin this manner the cutters y can be placed at three different distancesfrom the center to bore holes of as many different diameters. Thecutters 9 may, however, be made adjustable radially toward and from thecenter in any suitable manner other than that shown, in order that theymay be set to bore a hole of any desired diameter within the limits ofthe adjustment.

The rear portion of the stock A is turned down, and is provided with .ascrew-thread, 7c, over which turns a nut, D, against which bear theinner ends of the sliding cutters g, and

thus by turning this nut D forward or back ward on the screw-thread thecutters 9 may be adjusted longitudinally to cause them to project moreor less from the front end of the stock A, in accordance with thethickness of the metal to be bored or cut through. This longitudinaladjustment is an important advantage in a tool of this description, asit is always desirable to have the front ends of the cutters as near tothe face of the stock as pos sible, to afford a better support andrender them stiffer. Therefore, when a thin piece of metal is to bebored, the nut D can be turned to enable the cutters to be pushed in soas to project out only a sufficient distance to perform their work,while when a thicker piece is to be bored the nut can be turned toproject the cutters farther out, as required. This longitudinaladjustment of the cutters also enablesthem to be advanced as they becomeshorter from wear.

Z is a hole extending from the bottom of the drill-aperture c rearwardlythrough the shank b, through which a pin (not shown)v can be passed toforce out the drill B in case it should stick in the aperture 0, andthis pin, when removed from the hole Z, can be used to turn the nut Dbyplacing one end in the hole (1 or the set-screw (Z, the head of which isprovided with a hole, 1'.

It will be seen that each cutter, which is curved in the direction ofits width, as seen in Figs. 1 and 4, is thicker on one side than theother, causing the cutting-edge m to be of the greatest width, thecurved face of the cutter gradually diminishing in thickness from m toa, while the bottoms of the grooves e and f and the shoulders h arelower or nearer the center on one side than the other, which causes thecutters to beinclined slightly in the direction of their width, wherebythe inner curved surface of the cutter is made eccentric to the path ofrotation, and thus prevented from hearing against the inner wall of thegroove being cut in the metal, a perfect relief or clearance being thusafforded on both sides of the cutters, as shown by dotted lines in Fig.4, and undue friction thus avoided.

In using my improved boring-tool the center drill, B, is first set alittle in advance of the outer cutters, g, and clamped by means of theset-screw d. The tool is then rotated until the point of the drill haspenetrated the metal to a sufficient depth, as seen in Fig. 2, toprevent any possibility of its slipping, when the outer cutters, y, willbegin to act upon the metal to bore the hole by cutting an annularchannel in the metal, as above described, the center drill, B, servingas a guide to keep the tool in its proper central position while thecutters 1 are performing their work. As soon as the drill B has bored aguide-socket for itself of snfficient depth in the metal, theset-screw dis preferably loosened slightly to enable the drill B to be pressedfarther back into its socket c,

as the outer cutters, g, cut deeper into the metal, thus avoiding thenecessity of boring through the metal with the drill B, and consequentlyreducing to a minimum the power re quired to operate the tool, while theliability of either of the cutters falling through the metalwhen thehole is nearly bored and catchingis entirely avoided, thus preventingbreakage of the cutters from this cause-an event of frequent'occurrencewith tools of this description as heretofore constructed. The setscrew dmust, however, be adjusted to bear on the drill with sufficient frictionto prevent its point from slipping out of the socket first bored in themetal as the tool advances. If desired, a spring may be introducedbetween the set-serew d and the drill B, in order to produce a yieldingpressure thereon, which will render it easier to produce the necessaryamount of friction on the drill to keep its point in the cavity of themetal, and yet allow it to slide back as the tool advances.

By merely drilling a socket 0r guide-cavity with the center drill, B,instead of allowing it to bore entirely through the metal, a very greatadvantage is gained when drilling on a curved or uneven surface, as thedrill B serves to guide the outer cutters, g, both vertically andhorizontally, thus preventing them from following the curved or unevensurface of the metal, and also preventing a cutter from suddenlydropping into a blow-hole or flaw in the metal which might be exposed asthe cutters advanced, and thus interfere with the retation of thetool.It is obvious, however, that whenever desired the drill B may be allowedto remain tightly clamped in place within the stock A, to allow it tobore through the metal simultaneously with the outer cutters, g, andwhen a small hole of the same diameter as the center drill has beenpreviously bored and it is desired to enlarge it the drill B is firstdrawn out a little distance in advance of the cutters g and theninserted within the hole, when it will form a perfect guide for thetool, as the cutters bore the larger hole around and concentric with thesmall one, as required.

I am aware that cutters having the side on which the cutting-edge isformed of greater thickness than the opposite side are not new; hence Imake no broad claim to cutters of this description.

W'hat I claim as my invention, and desire to secure by Letters Patent,is-

1. In a metal-boring tool, the combination, with the stock A, having acentral guide-drill, B, made adjustable longitudinally in an axialsocket or aperture in said stock, of the outer cutters, made adjustablelongitudinally in suitable guideways, and the nut D, turning on ascrew-thread at the rear of the stock and bearing against the rear endsof the cutters 9, whereby the said cutters may be adjusted to projectmore or less from the face of the stock A, substantially as and for thepurpose set forth.

2. In a metatboring tool, the combination, with a stock, A, having acentral guide-drill, B, made adjustable longitudinally in an axialsocket or aperture in said stock, of the outer cutters, 1, madeadjustable longitudinally in suitable guideways in said stock, saidcutters being curved transversely and having the side on which thecutting-edge is formed of greater thickness than the opposite side,whereby a relief is formed, substantially as described.

3. In a metal-boring tool, the combination, with a stock, A, having acentral guide-drill, B, made adjustable longitudinally in an axialsocket or aperture in said stock, of the outer cutters, made adjustablelongitudinally in guide-grooves in said stock, said grooves having theirbottoms or shoulders lower or nearer the center on one side than theother, whereby the inner curved surfaces of the cutters are madeeccentric to the path of rotation, and said cutters having the side onwhich the cutting-edge is formed of greater thickness than the oppositeedge, whereby a relief or clearance is formed on both sides of thecutters, substantially as set forth.

\Vitness my hand this 13th day of December, A. D. 1886.

GEORGE W. TOWER.

I11 presence of P. E.TESCHEMAC1IER, A. G. DELANO.

